Changeset 2041 for draft-ietf-httpbis/latest/p1-messaging.xml

Timestamp:

08/12/12 08:00:42 (9 years ago)

Author:

fielding@…

Message:

remove irrelevant details from transforming proxy requirements now obsolete due to introduction of payload terminology; addresses #418

File:

• draft-ietf-httpbis/latest/p1-messaging.xml (modified) (2 diffs)

draft-ietf-httpbis/latest/p1-messaging.xml

@@ -2599 +2599 @@
 </section>
 
-<section title="Transformation" anchor="message.transformation">
+<section title="Transformations" anchor="message.transformations">
+<t>
+   Some intermediaries include features for transforming messages and their
+   payloads.  A transforming proxy might, for example, convert between image
+   formats in order to save cache space or to reduce the amount of traffic on
+   a slow link. However, operational problems might occur when these
+   transformations are applied to payloads intended for critical applications,
+   such as medical imaging or scientific data analysis, particularly when
+   integrity checks or digital signatures are used to ensure that the payload
+   received is identical to the original.
+</t>
 <t>
    If a proxy receives a request-target with a host name that is not a
@@ -2607 +2617 @@
 </t>
 <t>
-   A non-transforming proxy &MUST-NOT; modify the "path-absolute" and "query"
-   parts of the received request-target when forwarding it to the next inbound
-   server, except as noted above to replace an empty path with "/" or "*".
-</t>
-<t>
-   A non-transforming proxy &MUST; preserve the message payload (&payload;),
-   though it &MAY; change the message body through application or removal
-   of a transfer coding (<xref target="transfer.codings"/>).
-</t>
-<t>
-   A non-transforming proxy &SHOULD-NOT; modify header fields that provide
-   information about the end points of the communication chain, the resource
-   state, or the selected representation.
-</t>
-<t>
-   A non-transforming proxy &MUST-NOT; modify any of the following fields in a
-   request or response, and it &MUST-NOT; add any of these fields if not
-   already present:
-  <list style="symbols">
-    <t><x:ref>Allow</x:ref> (&header-allow;)</t>
-    <t><x:ref>Content-Location</x:ref> (&header-content-location;)</t>
-    <t>Content-MD5 (<xref target="RFC2616" x:fmt="of" x:sec="14.15"/>)</t>
-    <t><x:ref>ETag</x:ref> (&header-etag;)</t>
-    <t><x:ref>Last-Modified</x:ref> (&header-last-modified;)</t>
-    <t><x:ref>Server</x:ref> (&header-server;)</t>
-  </list>
-</t>
-<t>
-   A non-transforming proxy &MUST-NOT; modify an <x:ref>Expires</x:ref>
-   header field (&header-expires;) if already present in a response, but
-   it &MAY; add an <x:ref>Expires</x:ref> header field with a field-value
-   identical to that of the <x:ref>Date</x:ref> header field.
-</t>
-<t>
-   A proxy &MUST-NOT; modify or add any of the following fields in a
-   message that contains the no-transform cache-control directive:
-  <list style="symbols">
-    <t><x:ref>Content-Encoding</x:ref> (&header-content-encoding;)</t>
-    <t><x:ref>Content-Range</x:ref> (&header-content-range;)</t>
-    <t><x:ref>Content-Type</x:ref> (&header-content-type;)</t>
-  </list>
-</t>
-<t>
-   A transforming proxy &MAY; modify or add these fields to a message
-   that does not include no-transform, but if it does so, it &MUST; add a
-   Warning 214 (Transformation applied) if one does not already appear
-   in the message (see &header-warning;).
-</t>
-<x:note>
-  <t>
-    <x:h>Warning:</x:h> Unnecessary modification of header fields might
-    cause authentication failures if stronger authentication
-    mechanisms are introduced in later versions of HTTP. Such
-    authentication mechanisms &MAY; rely on the values of header fields
-    not listed here.
-  </t>
-</x:note>
+   A proxy &MUST-NOT; modify the "path-absolute" and "query" parts of the
+   received request-target when forwarding it to the next inbound server,
+   except as noted above to replace an empty path with "/" or "*".
+</t>
+<t>
+   A proxy &MUST-NOT; modify header fields that provide information about the
+   end points of the communication chain, the resource state, or the selected
+   representation. A proxy &MAY; change the message body through application
+   or removal of a transfer coding (<xref target="transfer.codings"/>).
+</t>
+<t>
+   A non-transforming proxy &MUST; preserve the message payload (&payload;).
+   A transforming proxy &MUST; preserve the payload of a message that
+   contains the no-transform cache-control directive.
+</t>
+<t>
+   A transforming proxy &MAY; transform the payload of a message
+   that does not contain the no-transform cache-control directive;
+   if the payload is transformed, the transforming proxy &MUST; add a
+   Warning 214 (Transformation applied) header field if one does not
+   already appear in the message (see &header-warning;).
+</t>
 </section>
 </section>